I don’t know the answer to that question, but we are well on our way to finding out.
Although growing fish and plants together in ponds has been around since the dawn of agriculture, aquaponics is a fairly new technique for cultivating food in contained aquatic systems. Combining the science of aquaculture and hydroponics, aquaponics utilizes natures cycles, like fish waste becoming food for plants.
In the Paradise Lot Bioshelter, we’re also experimenting with “food chains”. 1) A plankton “refugium”, or tank lacking predators, spills into the next tank. In this next 2) fish tank corralled livebearing gambusia fish (a type of guppy), hatch their young which fall through a net into another net housing breeding goldfish. When the goldfish babies hatch they swim out through a cage into the tank were the bullhead catfish live. Omnivores, these catfish then have the opportunity to eat the baby goldfish. The next 3) grow out tank houses live bearing crayfish and clams, both of which add to the fish food diversity and help to feed the baby fish that spill here from tank two. Ultimately we humans are the top of the food chain. A late summer catfish fry is an exciting prospect!
The feederfish don’t breed every day, so we will still need to supplement with catfish pellets. We hope to also feed the catfish red wiggler worms and black soldier fly larvae produced in the bioshetler.
The picture above shows one of two gravel beds (half 55 gal drum) that hang above the tanks. The gravel in the beds are the primary filtration for the system, turning fish waste into plant fertilizer. Plants can grow right in the gravel, while water washes over their roots for 15 minutes every hour. The water drains out of the gravel beds, back into the fish tanks, between each interval pulling oxygen into the root zone of the plants. Red wiggler earth worms can be grown in these beds, helping to break down the fish waste solids, offering more food for the plants. One gravel bed is filled with expanded shale, the other with biochar.
Stay tuned for more interesting permaculture greenhouse aquaponics!